Method of distilling oils



June 29, 1937. F. L. FAST METHOD DISTILLING OILS Filed Deo. 4, 1955patented June 29, '1937 METHOD F DISTILLING OILS Fred L. Fast, Woodbury,N.

cony-Vacuum Oil Company, New York, N. Y., a corporation J., assignor toSo- Incorporated, of New York Application December 4, 1935, Serial No.52,755 4 Claims. '(Cl. 19d- 73) This invention relates' to methods ofdistillatiiclin of the heavier fractions of crude petroleum o s.

.Considerable difilculty is encountered in obtaining full yields of theheavier viscous distillates, particularly from crudes of a mixed base orasphaltic base nature in which the oils heavier than those whoserecovery is desired are of an asphaltic nature. Batch fractionaldistillation, by shell stills or other methods taking narrow vapor cutsat increasing temperature levels are objectionable, even when carriedout under vacuum, because of the combination of temperature and timeelements of sucha nature as to lead to serious decomposition of thedesired fractions. Flash distillations, with or without steaming, atatmospheric pressure or under vacuum, are effective insofar as they areable to reduce ex'posure to conditions which promote decomposition, butsince the heat for the vaporization vof desired constituents must comefrom the sensible heat of the flash stream, vaporization occurs in aregion of rapidly falling temperature, and dangerously high heat levelsare necessary to attain good recovery,

in damage to the stock distilled, even under high vacuum and/or in thepresence of considerable steam. It has been proposed to accomplish thesupply of sufficient heat at a sufficiently high level to give desiredvaporization by recirculation of residuum through the heater in companywith the charge. Even this has not been able to accomplish the desiredpurpose in some instances, and resort has been had to adding a lightvolatile material of the nature of gas oil or kerosene to the charge oilentering the heater in order to take advantage of its carrying effect inthe subsequent vaporlzation. The addition of this material adds to theheat load necessary to accom- 0 plish a given distillation, and itsseparation and recovery calls for additional fractionation andcondensing equipment. The object of this invention is to reduce the.temperature level which must be carried to accomplish a desiredvaporization of heavy distillates, without including in the charge ofoil to be heated a carrier material of nature widely diering from thatwhich it is desired to recover in the particular distillation step. Afurther ob- 5ject is to obtain a proper additional carrying effeet ofvapors lighter than the heaviest oil'recovered as distillate, withoutintroducing to the distillation system an oil which is foreign in natureto the oils handled therein, and without the these heat levels oftenresulting` expenditure of additional heat to create those lightervapors.

It is a feature of this invention that an oil comprising a longresiduum, i. e. containing some gas oils, light and heavy lubricants,and whatever asphaltic residual matter is present in the crude, is firstsubjected to ash distillation to remove the greater portion of thedesired material as vapors. The remainder, stripped of the greaterproportion of vaporizable fractions, but at a lowered temperature due tothe loss of heat absorbed by vaporization of the lighter fractions, iscirculated through a heater to regain temperature and vaporized in sucha way that advantage is taken of the carrying effect of the vaporspreviously formed. The reheated oil, now carrying a much smallerproportiony of vaporizable to nonvaporizable material, will not lose asmuch temperature onI flashing as the original mixture. The highertemperature thus prevailing is vconducive to the vaporization offractions of higher boiling point than vaporizable by the iirst ashing.

It is a further feature of this invention that the sensible heat carriedby the residue of this second vaporization step is further used toimpart heat to the cooler residue of the rst vaporization step, whichheat is imparted and dissipated with a minimum time element, therebysecuring maximum vaporization with high heat economy and a minimum ofdecomposition.

It is a further feature of this invention that the final temperature ofthe residue of the second flashing step may be controlled by controllingthe proportionof vaporizable to non-vaporizable materials present in thestream before the secondary vaporization occurs. f It is a furtherfeature of this invention that vapors of similar nature, destined forcommingling in the same final product, but originating in separatevaporization operations, are so handled that they may be fractionatedand condensed together, resulting vin marked economies of equipment fora given recovery of distillate.

Other features of the invention consist of certain novel modes ofoperation hereinafter described and particularly defined in the claims.

4This invention is herein described as being.

.pertinent to the recovery of heavy lubricating stock from the asphalticresidue of a mixed base crude. It is not limited to such use, but may beused for the separation of oils of high boiling point whether theresidue be asphaltic or not, as Well as for other uses hereinafterpointed out. The vaporization steps of this invention may A be carriedout at atmospheric pressure, or under mum temperature with less vacuumand/or steam. With set limits of temperature and of vacuum and/or steam,it will permit the recovery of greater amounts of distillate for a givenheat input.

This invention, as directed to the recovery of heavy lubricating oildistillates, is operated upon topped crude oil. That is, the chargingstock to the distillation process is a crude oil from which gasoline,kerosene, and more or less` gas oil have already been removed by aprocess of distillation as a step in preparation for the process of.this invention. This topped crude, if `from a mixed base oil, to whichthis invention is most applicable, will contain, in addition to thelight and heavy lubricants ,which are desired, an asphaltic material tobe rejected as residue and more or less gas oil lighter than the desiredlubricant fractions. It may contain only the amount of gas oil normallyrecovered with and considered a part of the wax distillate cut, or itmay contain more than that amount if desirable for its carrying effectin flash vaporization.

In ,orderl that this invention may be more thoroughly understood,reference is made to the drawing which is attached to and made a part ofthis specification. 'I'he single gure of this drawing shows indiagrammatic form an apparatus suitably equipped for carrying out thisinvention.

In the drawing, I designates a furnace or pipe still heater, and 2 thelower portion of a fractlonating tower. Topped crude oil charge, underpump pressure, enters the furnace I through inlet 3 and passes throughconvection coils and roof coils 5, to leave through transfer line S,entering fractionating tower 2 in ash chamber l. If desired a backpressure may be held upon the heating coil by control of'valve 8. Uponentry of the heated topped crude to the ash chamber l, a considerableportion, determined by the temperature in transfer line 6 and the natureof the charge, will vaporize, and rise through chimney 9 past drawoi`plate I0, to continue upward through tower 2. Unvaporized residue willpass downward through bailles ii to storage space I2, into which steamis led through pipe I3. This steam in passing through the oil in I2 andupward in contact with the oil passing baiiies II, will exert astripping action thereon. This much of the operation is substantiallyidentical withprior practice. As explained, due to conditions of heatdrop in chamber 'I and across baiiles Il, it is dificult to get completevaporization of heavy lubricant fractions, even with the aid of steamfrom i3, without unduly high temperatures in transfer line 6.

In practice according to this invention, no attemptis made to getcomplete vaporization by means of high heat level in transfer line 6.Instead, residue from I2 is withdrawn through pipe I4 by pump I5, forcedthrough coils I6 placed on the walls of the combustion chamber of thefurnace I, and delivered through transfer line AIl to Hash plate I 8located in tower 2 above flash chamber l. If desired back pressure maybe held on this heating cycle by control of valve I9. Ailditionalvaporization will take place on flash plate i8, and the oil not thereonvaporized will drop through one or more stripping plates 2W, where it iscontacted with light vapors from the rst vaporization, collect ondrawoff plate I and pass through tube 2I and over bales II to storagespace I2. The operation of this cycle is so conducted that the amounthandled by pump I5 and heated per unit of time is much greater than theamount of residue from crude unvaporized in lduring the same unit, oftime. That is, there is a continuous circulation of completely Istrippedasphaltic residue through I5, I6, I'l, I8,

20, I0, 2|, I2 to which is added a small amount of fresh incompletelystripped residue from chamber ll.

The present invention is an advance over prior practice in several veryimportant respects.

Heavy oil fed to ash plate I8 contains enough heat storage medium sothat such vaporization as occurs there is without substantial loweringof temperature. Heavy oil leaving flash plate I8 is at a hightemperature, and is immediately contacted, at stripping plate 20, withlight vapors and steam from ash chamber I, and by them further stripped.The stripping action so accomplished is of suiiicient magnitude so thatfor a certain temperature in transfer line I'I, a much lower proportionof heat-carrying medium will give an equivalent vaporization, or withthe same proportion of heat carrier, a lower temperature maybe used. Atthev temperature levels necessary for vaporization of oils of thisnature, even small differences of temperature are of major importance.

As a second feature of very considerable economic importance, all vaporspass together into the upper portion of tower l2, which is equipped withfractionation equipment of any 'type'suit'' able, the functioning ofwhich has nothing to do with this invention, and which is here omittedfor simplicity.

'I'he heavy, unvaporized hot oil from ash plate i8, after passingthrough and being stripped on stripping plate 20, collects on drawoplate ill. 'I'hat portion of it which is desired to be recovered asresiduum is drawn through pipe 22 for removal from the system. Ii'desired, thisv oil may be further concentrated by use of a strippingtower of the usual sort 23, from which nal tar product is withdrawn tostorage through pipe 24. The oil passing from drawoi `plate ID throughpipe 2l has a further very useful duty to perform. It is at a muchhigher temperature than the residue from ash chamber 1, and isimmediately mixed with that residue, and passes with it over baffles Ilin contact with steam from i3. In this manner, arsource of heat at ausefulhigh level is available for the stripping of the otherwise rapidlycooling residue from flash chamberV l. And, most important, that heat isavailable at a level which will not cause decomposition of valuableconstituents in the residue from ash chamber 1.

Taken together, the new concepts present in.

'following steps: heating maximum temperature limitation combined with arequirement for maximum yields. As an example of one such application,the finishing distillation of treated pressure distillate may be noted.

I claim:

l. The method of distilling an oil susceptible to decomposition -eiectsabove a certain temperature to obtain therefrom a full yield ofuncracked distillate products which comprises the the oilv in a confinedstream to a temperature near, but substantially below its crackingtemperature level, passing it to a vaporizing step and separating vaporsfrom liquid oil, mixing the liquid oil with a hydrocarbon heat carrierwhich is at a higher temperature still below the cracking temperaturelevel of constituents the mixture with steam to cause vaporization of afurther portion of the liquid oil, heating the mixture in a secondconfined heating stream to a temperature close to the crackingtemperature level of constituents of the first oil, passing the heatedmixture to a vaporizing step to separate vapors and leave a residuum,contacting the residuum with vapors and steam from the rst va porizationto effect removal of a final portion of vapor therefrom, removing aportion of residue from the system, and mixing the remainder with liquidoil from the rst vaporization as a heat carrier therefor.

2. The method of claim 1 in which the vaporization and stripping stepsare conducted under reduced pressure.

3. The method of claim 1 in which the proof the first oil, contactingvportion of heat-carrying residue added to liquid oil from the firstvaporization is suihciently great so that no substantial drop intemperature occurs during the second vaporization. Y

4. The method of recovering a full yield of un cracked lubricatingdistillate from a mixed base crude oil without subjecting the oil totemperatures suiliciently great to cause substantial loss of thelubricant oil fraction by decomposition which comprises the followingsteps: heating a long residuum in a confined stream to a temperaturesulcient to cause vaporization of a substantial portion of the lubricantdistillate, flashing the heated oil to separate vapors from liquid oil,admixing the liquid oil with asphalt which is at a higher temperature,contacting the mixture with steam to vaporize further lubricatingdistillate, heating the mixture in a second co'nfined stream to atemperature high enough to vaporize substantially all the remaininglubricating distillate, this temperature being higher than that ofpreceding heatings, but not suciently high to bring about substantialcracking of unvaporized constituents of the long residuum, dashing theheated mixture to separate lubricating distillate vapors and a residualasphalt, contacting the residual asphalt with vapors and steam from therst vaporization to insure complete stripping of lubricating distillatetherefrom, removing a portion of the asphalt from the system, and mixingthe remainder with the liquid oil from the rst vaporization as a heatcarrier therefor.

FRED L. FAST.A

